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Re: birthpoints in rtl.
- From: Diego Novillo <dnovillo at google dot com>
- To: Kenneth Zadeck <zadeck at naturalbridge dot com>
- Cc: gcc <gcc at gcc dot gnu dot org>, "Bonzini, Paolo" <bonzini at gnu dot org>, "Park, Seongbae" <seongbae dot park at gmail dot com>, Ian Lance Taylor <iant at google dot com>, Richard Sandiford <rsandifo at nildram dot co dot uk>, Steven Bosscher <stevenb dot gcc at gmail dot com>
- Date: Fri, 29 Feb 2008 17:46:45 -0500
- Subject: Re: birthpoints in rtl.
- References: <47C5EF2A.5020401@naturalbridge.com>
On 2/27/08 6:15 PM, Kenneth Zadeck wrote:
Comments? Volunteers?
How about adding FUD chains instead of the dense UD chains we have
today? FUD chains are almost trivial to port from gimple-ssa into RTL.
We already overlay a use-def web on the RTL representation using the new
dataflow bits.
Unless I'm missing something obvious, we could easily convert those
dense chains into factored chains by inserting real PHI nodes and
building a FUD chain web.
The code to compute insertion points is almost totally independent from
the IL (it should not be hard to adapt to the DF def/use
representation). We just need to have a way of representing PHI nodes.
No changes to the RTL representation should be necessary.
We could even adapt the global live-in computation to prune the
dominance frontiers. But that's just an optimization.
I may be able to spend some time on this.
Diego.